Power assisted safety gate

ABSTRACT

A power assist comprising a pivotable handle member, a switch unit and an electromagnetic linear motor unit for use particularly in association with a safety gate of the type used on plastic injection molding machines or the like. Manually applied force on the handle member to move the safety gate from a closed position will energize the linear motor in one direction to assist in movement of the gate, and force on the handle member in the other direction will reverse the linear motor to assist in moving the gate to its closed position.

United States Patent [1 1 Chaisson Oct. 2, 1973 [54] POWER ASSISTED SAFETY GATE 1,684,704 9/1928 Hubbell 49/32 X 1,950,627 3/1934 Parvin 49/360X [751 inventor: n' Sprmgfleld, 2,926,013 2/1960 Dongen 49 32 ass.

[73] Assignee: Package Machinery Company, East P i E i r j, Karl Bell Longmeadow, Mass. AttorneyMcCormick, Paulding and Huber [22] Filed: Oct. 2, 1969 Appl. No.: 863,047

57 ABSTRACT A power assist comprising a pivotable handle member, a switch unit and an electromagnetic linear motor unit for use particularly in association with a safety gate of the type used on plastic injection molding machines or the like. Manually applied force on the handle member to move the safety gate from a closed position will energize the linear motor in one direction to assist in movement of the gate, and force on the handle member in the other direction will reverse the linear motor to assist in moving the gate to its closed position.

1 Claim, 6 Drawing Figures PATENIEU m 2 SHEEI 10F 2 QNVENTOR WILLIAM P CHAISSON ATTORNEYS POWER ASSISTED SAFETY GATE BACKGROUND OF INVENTION Some plastic injection molding machines are very large and have heavy safety gates which are tiring to operate, and a tired operator is disposed to carelessness and even to operate the machine by some means with an open safety gate. The hazards of such carelessness are obvious, and it can be used that it is the general object of this invention to provide a power'assist for the operator of such safety gates to reduce substantially the labor of their operation and thereby similarly to reduce the temptation for careless operation.

SUMMARY OF THE INVENTION In keeping with the present invention, a simple power assist structure is provided for association with a sliding safety gate or door for a plastic injection molding machine or the like. The said structure includes a handle for the gate which is pivotally mounted on it to actuate a switch unit, also mounted on the gate or door. The gate further supports an electromagnetic unit comprising a part of a linear A.C. excited induction motor which includes an elongated rod mounted on the machine frame. The said electromagnetic unit may be a coil or other distributive winding or the like capable of producing eddy currents and phase shifting as in a single or three-phase induction motor. The said electromagnetic unit is connected through the said switch unit to a power supply, and when the switch is actuated by movement of the handle in one direction, as to open the gate, the electromagnetic unit is energized to operate in one direction, that is, to move along the rod in the gate opening direction. When the handle is moved in the opposite direction, as to close the gate, the switch unit is actuated in the opposite direction to reverse or switch the phase of the linear motor and to reverse the direction of movement of the electromagnetic unit along the rod. It is to be understood that the rod may be mounted on the door and the winding on the machine frame without change in the operating principle of the invention.

A reversible linear motor of the type referred to is manufactured and sold by Skinner Precision Industries of New Britain, Connecticut, under the trademark POLYNOID.

The handle is biased to a neutral position wherein the switch unit is not engaged and the linear motor is not energized. It is only when the handle is gripped by an operator and force is applied to it as though to open or close the gate manually, that the linear motor is energized to provide a power assist to movement of the gate in the desired direction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view ofa safety gate embodying the present invention.

FIG. 2 is a vertical sectional view taken generally along the line 22 of FIG. 1 but with some parts shown in elevation.

FIG. 3 is an enlarged view of the lower portion of the handle shown in FIG. 2.

FIG. 4 is a sectional view taken generally along line 44 of FIG. 3.

FIGS. 5 and 6 are enlarged views similar to 3 and 4, but showing a modified handle mounting.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 the reference number 10 indicates generally a rectangular safety gate or door having a viewing window 12 so that the operator of a plastic injection molding machine or the like upon which the gate or door 10 is mounted canview the operation of the machine with the gate closed. The gate is shown in the closed position and is to be moved toward the left to be opened and returned to the closed position by operation of a handle 14. In order to accommodate such sliding opening and closing movement, the gate 10 has a plurality of upper and lower rollers 16 and 18, which are appropriately mounted on the said gate to ride upon elongated horizontally disposed upper and lower track members 20 and 22 which are mounted on the machine frame by upper and lower brackets 24 and 26, respectively. The door per se and its operation as a safety device for a plastic injection molding machine or I the like may be as shown in the Weiner U. S. Pat. No. 3,386,133 of June 4, 1968.

As has been said, the gate or door 10 used on large plastic injection molding machines may be very heavy and tiring to operate, and, therefore, a power assist is provided in accordance with the present invention. The said power assist comprises an A.C. excited linear electric motor indicated generally by the reference number 28 in FIGS. 1 and 2. This motor includes a stacked electromagneticunit 30 supported on the gate or door 10, preferably at the bottom thereof, on a mounting bracket 32 and a horizontally disposed rod 34 supported at its ends on brackets such as the bracket 36 extending from the frame of the machine. As mentioned before, the stacked electromagnetic unit 30 is designed to provide eddy currents and to be reversed as to its direction of influence by phase shifting control.

The construction of the linear motor 28 is not a part of the present invention, such motors being commercially available as previously mentioned. However, it is to be noted that the force or assist to movement of the gate 10 can be adjusted by adding and substracting stacks to the electromagnetic unit 30. Thus, for a gate of known weight, the electromagnetic unit 30 can be made up to require only a preselected manual force on the handle 14 to move the gate toward open or closed position, the rest of the force being applied by the linear motor 28. It is a property of such motor that when it is energized for operation in.one direction, the electromagnetic unit 30 (which is normally considered the stator in a conventional motor) will move along a rod such as the rod 34 (which is normally considered to be the armature in a conventional motor) until the door 10 or the unit 30 engages a stop. Similarly, when the motor 28 is energized out of the initial phase, the unit 30 will move along the rod 34 in the opposite direction until the door or unit reaches a stop.

According to the present invention, the vertically elongated handle 14 is pivotally mounted on the gate or door 10 so that it can be gripped by the operator and moved toward the normal door opening or closing directions with a predetermined force such as will cause it to actuate the linear motor 28 and bring its power assist into play in moving the said door or gate. More specifically, and as shown in FIGS. 1, 2 and 3, the handle 14 is mounted on the outwardly projecting ends of generally similar upper and lower support arms 38 and .40,

respectively. The support arms 38 and 40 extend through suitable openings in the gate and are pivotally mounted between their ends on similar pivots supported on the inside of the door, each of which is indicated generally by the reference numeral 42 in FIGS. 2 and 3. The handle 14 can be used for wholly manual movement of the gate or door 10. That is, without electrical power assist the handle support arms 38 and 40 will engage the side edges of their associated slots through the door to limit the pivoting movement of the handle relative to the door and cause door movement with continued force on the handle. I

The lower handle mounting arm 40 has a bifurcated inner end portion, best shown in FIGS. 3 and 4, which straddles a switch actuating finger or whisker 44 associated with a switch unit indicated generally by the reference number 46. It is important to note that when the handle 14 is gripped and forced by the operator in the direction tending to open the gate 10 manually, the lower arm 40 will be moved in a clockwise direction as viewed in FIG. 4, and when the handle is forced in the opposite direction, the arm 40 will be pivoted in a counterclockwise direction. It is also important to note that the handle 14 is biased to a neutral position, such as shown in FIG. 4, by a pair of springs 48, 48 mounted on brackets 50, 50. Thus, whenever no force is applied manually to the handle 14, it will be returned to a neutral position by the said springs 48, 48 which are both connected to a pin 52 extending upwardly from the lower handle arm 40.

While the switch unit 46 may be provided in various specific forms, in the preferred embodiment, it comprises a single unit having two pairs of poles which are normally open (in the neutral position of the handle 14 and finger 44), the poles being connected in different lines from a source of A. C. electrical energy to the electromagnetic unit 30. That is, the switch unit is so designed that when the handle 14 is in its normal position, as determined by the bias of the springs 48, 48, no energy is passed to the unit 30. However, when a force is applied to the handle 14 tending to open the gate or door 10, one set of poles is closed by movement of the finger 44 in one direction caused by clockwise pivoting movement of the handle arm 40 as shown in FIG. 4 to energize the unit 30 to move it and thus the gate or door 10 toward the left as viewed in FIG. 1, applying the assist force to the manual operation of the handle. When the handle 14 is moved in the opposite direction, the position of the switch actuating finger 44 is shifted in the opposite direction thus to close the other set of poles and shift the phase of energization of the electromagnetic unit 30 to cause it to move toward the right relative to the rod 34 and thus to apply the assist to movement of the door 10 toward the right or toward the closed position. Therefore, according to the present invention, whenever the operator engages the handle 14 and applies a predetermined force to it, the electric motor assist comes into play in moving the gate, and whenever the operator releases the handle, the assist is removed so that the door can quickly come to rest. To complete this understanding of the operation, it is to be noted that the switch unit 46 is electrically connected to the electromagnetic unit 30 by a conductor cable 54 extending along the door 10 to a terminal box 56 mounted on the front surface of the door, and this terminal box has a conductor cable 58 connecting it to the unit 30, all as shown in FIGS. 1 and 2.

While not shown in the drawings, a limit switch is included in the power line to the linear motor 28, the said limit switch being normally closed but being positioned to be engaged by the door when it is fully closed. When thus engaged by the door, the said limit switch is opened so that there will be no energy transmitted to the linear motor if the operator should continue to apply force to the handle 14 in the closing direction. This will prevent an electrical overload on the linear motor. Similarly, when the door 10 is fully opened, it will engage a switch which energizes a timer operable to open the power circuit after a timed interval if the operation should continue to hold the handle in a door opening position. This also prevents electrical overload on the linear motor 28.

In FIGS. 5 and 6 there is shown a modified mounting for the handle 14 on the door 10 which still enables it to operate the switch actuating finger 44. In the said modified form, the bottom end of the handle 14 is mounted on the forwardly or outwardly projecting end of an arm 60 which is pivotally supported on a pin 62 threaded into a block 64 secured to the inner surface of the door 10, the said pin extending upwardly from the block. The upper end of the door handle is similarly mounted on a similar arm. It will be noted that the inner end portion of the arm 60 is provided with an aperture 66 which receives the upwardly projecting end portion of the switch actuating finger 44.

The handle and arm unit 14, 60 is biased to its normal or neutral position shown in full lines by a torsion spring 68 which is coiled around a bushing 70 on the pivot pin 62 above the arm 60. The ends 72 and 74 extend inwardly of the door 10 over the arm 60 and are pinched toward each other to preload the spring 68, and the said ends are trapped between a pair of pins 76, which are mounted in and project downwardly from the horizontal portion 78 of an angle bracket having a vertical portion 80 which is secured to the inside of the door 10 in spaced relationship over the handle arm 60.

The end portions 72 and 74 of the said spring 68 are also engaged by a pair of spaced apart upwardly extending pins 82 and 84, respectively, the said pins being secured in the inwardly projecting end portion of the handle arm 60. Thus, when the arm 60 is pivoted in a clockwise direction by the handle 14 as viewed in FIG. 6, the pin 82 will move the spring end 72 also in a clockwise direction placing a load on the spring 68 tending to return the handle 14 and arm 60 to the neutral or solid line position shown. When the arm 60 is moved in the counterclockwise direction by the handle 14 as to close the door 10, the pin 84 will move the spring end 74 also in a counterclockwise direction loading the spring 68 so that it will tend to return the handle 14 and arm 60 to the normal or neutral solid line position shown. The limit of clockwise movement of the handle and arm is set by a vertically upwardly projecting pin 86 carried on the block 64 to engage the side of the arm 60, and a similar pin 88 limits the counterclockwise movement of the arm and handle.

I claim:

1. A power assist for manual movement of a horizontally sliding safety door mounted on a plastic injection molding machine or the like, the said assist comprising a reversible direction linear motor including a relatively movable electromagnetic induction current producing unit and an elongated rod, one of which is mounted on the door and the other of which is mounted on the machine for relative movement parallel to the desired door movement, and means for controlling said linear motor including a substantially vertically disposed handle (movably) mounted on said door for limited pivotal movement on a substantially vertical axis in operator use as in wholly manual door operation, the handle movement relative to said door during operator use being generally parallel to the direction of desired door movement, a control switch unit connected between said linear motor and a source of electrical energy and operable by said handle in one direction of movement thereof parallel toand in the direction of door opening movement to provide an assist for door opening and in the other direction to reverse operation of the motor to assist in door closing, said control switch unit including an actuating finger engaged and operable by said handle and arranged to be displaced only by movement of said handle from a neutral position in either its said one or other direction to energize said motor for operation in one direction and to reverse it, respectively, and means biasing said handle to said neutral position whereby an assist is applied to movement of said door only by an operator tending to move the door in a desired direction by application of a determinable force to said handle.

8 I! i t t 

1. A power assist for manual movement of a horizontally sliding safety door mounted on a plastic injection molding machine or the like, the said assist comprising a reversible direction linear motor including a relatively movable electromagnetic induction current producing unit and an elongated rod, one of which is mounted on the door and the other of which is mounted on the machine for relative movement parallel to the desired door movement, and means for controlling said linear motor including a substantially vertically disposed handle (movably) mounted on said door for limited pivotal movement on a substantially vertical axis in operator use as in wholly manual door operation, the handle movement relative to said door during operator use being generally parallel to the direction of desired door movement, a control switch unit connected between said linear motor and a source of electrical energy and operable by said handle in one direction of movement thereof parallel to and in the direction of door opening movement to provide an assist for door opening and in the other direction to reverse operation of the motor to assist in door closing, said control switch unit including an actuating finger engaged and operable by said handle and arranged to be displaced only by movement of said handle from a neutral position in either its said one or other direction to energize said motor for operation in one direction and to reverse it, respectively, and means biasing said handle to said neutral position whereby an assist is applied to movement of said dooR only by an operator tending to move the door in a desired direction by application of a determinable force to said handle. 